Increased demand for large scale synthesis of in vitro transcribed (IVT) mRNA is being driven by an increasing use of mRNA for transient gene expression in ex vivo cell engineering or direct in vivo therapeutic applications. One of the most important determinants of potency of an IVT mRNA is the 3′ poly-adenosine (poly(A)) tail, the length of which directly correlates with efficiency of translation. However, present methods for large scale generation of IVT mRNA rely on templates derived from circular plasmids, in which homolypolymeric tracts are highly unstable, thus limiting encoded poly(A) tail lengths to less than approximately 120 base pairs. Thus methods are needed to generate mRNA that are highly stable for translation.